First Group Of Rats Research Articles

Anti-Inflammatory Effects of Specific Cyclooxygenase 2,5-Lipoxygenase, and Inducible Nitric Oxide Synthase Inhibitors on Experimental Autoimmune Anterior Uveitis (EAAU)

Purpose: Inflammation, in general, causes the release of a variety of inflammatory mediators that in turn induce cyclooxygenase (COX) 2, nitric oxide synthase (iNOS) and 5-lipoxygense (LP) synthesis, producing large amounts of inflammatory prostaglandins (PG), nitric oxide (NO), and leukotriene (LT) B4. Therefore, inhibition of these enzymes may abrogate intraocular inflammation in experimental autoimmune anterior uveitis (EAAU). Methods: Lewis rats were immunized with melanin-associated antigen (MAA) isolated from bovine iris and ciliary body. These animals were divided into three groups. The first group of rats received subcutaneous injection of COX 2 inhibitor CS 236 at different time points. The second and third groups of animals received subcutaneous aminoguanidine (AG), an iNOS inhibitor, and nordihydroguaiaretic acid (NDGA), a 5-LP inhibitor, respectively. Control animals received vehicle. Rat eyes were examined daily by slit-lamp biomicroscopy from Day 7 to 30 post injection for uveitis. Animals were also sacrificed at various time points for histologic analysis. Results: Control animals developed severe EAAU in both eyes. The disease started in these animals on Day 12 post immunization and lasted for ten days. Interestingly, CS 236, a potent COX 2 inhibitor, completely abrogated EAAU when the animals were treated daily from the Day 0 to 14 or Day 0 to 20 after MAA injection. Furthermore, daily CS 236 treatment after the onset of EAAU (Day 14–20) significantly reduced the severity (both clinical and histologic) of EAAU and shortened the duration of disease. iNOS inhibitor (AG) and 5-LP inhibitor (NDGA) partially attenuated EAAU. Conclusions: Our results show that EAAU was partially attenuated by AG and NDGA. Interestingly, CS 236, a potent COX 2 inhibitor, completely inhibited EAAU in male Lewis rats most likely by inhibiting the initial phase and onset of the disease.

Antibiotic Administration in an Animal Model of Chronic Peritoneal Dialysate Exposure

♦ Objectives The high incidence of intraperitoneal infection remains an important problem in animal models of chronic dialysate exposure. Prophylactic antibiotic administration can be used to resolve this problem, but the isolated effects of antibiotics on peritoneal membrane function and structure are unknown. The present study examined the effects of prophylactic antibiotics on infection rate and peritoneal membrane function and structure in a rat model of chronic dialysate exposure. ♦ Design A first group of rats (A; n = 12) received 10 mL 3.86% glucose dialysate twice daily through a heparin-coated catheter. In a second group of animals (B; n = 12), oxacillin 2.5 mg/day and gentamicin 0.04 mg/day were added to the dialysate. Group C ( n= 12) was injected twice daily with an identical dose of antibiotics dissolved in 1 mL of buffer solution. Group D ( n = 12) was left untreated. Dialysate cultures were obtained regularly. After 8 weeks of exposure, peritoneal transport studies were performed and samples for histology were obtained. ♦ Results Technique survival was 92% in group A and 100% in the remaining groups. Five rats in group A but none of the animals in the other groups developed peritonitis. The transport rates of small solutes were elevated and net ultrafiltration was decreased in group A compared to the controls. Fibrosis, as evaluated by quantifying Picro Sirius Red staining with image analysis, was significantly elevated in group A (3.48% ± 1.06% vs 0.72% ± 0.51% in group D, p < 0.05) but not in group B (0.29% ± 0.07%) or in group C (0.52% ± 0.28%). Vascular density, measured by counting the number of blood vessels that stained positive for endothelial NO synthase, was increased in both groups that were exposed to dialysate: 153.0 ± 12.9/μm2 in group A and 131.6 ± 14.3/μm2 in group B, versus 76.76 ± 12.37/μm2 in group C and 73.2 ± 10.4/μm2 in group D ( p < 0.01). ♦ Conclusions Prophylactic administration of oxacillin and gentamicin adequately prevented intraperitoneal infection in an animal model of chronic dialysate exposure. In addition, fibrosis was absent, suggesting intra-peritoneal infection rather than dialysate exposure is a causative factor.

Assessment of therapeutic effect of Inula heterolepsis Boiss in alcoholic rats.

An aqueous extract from the root of Inula heterolepsis Boiss was prepared and then tested for its ability to treat experimentally induced alcoholic hepatic injury in rats. Alcoholic rats were divided into two groups. The first group of rats were given 200 mg/kg/day plant extract. Repeated doses of extract preparations were given at 12 h intervals for 10 days. Differences between the recovery of tissue injury, with and without Inula plant extract, were evaluated. The second group of rats were given vehicle. Liver, testis and kidney injuries due to the chronic alcohol consumption were proven biochemically and histopathologically. Rats were killed, serum SGOT, SGPT, alkaline phosphatase, and albumin levels were measured. SGOT, SGPT and alkaline phosphatase levels were significantly higher in alcoholic rats due to the tissue damage compared with intact, vehicle and Inula treated groups of rats (p < 0.05). Liver, testis, kidneys, stomach, intestine, heart, lungs and bladder were examined histopathologically. According to our study, the root extract of Inula heterolepsis Boiss has a slight therapeutic effect on alcoholic liver, kidney and testis damage in rats. Comparing the therapeutic effects in these organs, the liver seemed to be affected meaningfully after treatment with the plant extract.

Compared effects of hindlimb unloading versus terrestrial deafferentation on muscular properties of the rat soleus

Hindlimb unloading is known to induce some neuromuscular changes especially in postural muscles such as the soleus. Our goal was to determine the role of proprioceptive inputs on these modifications by comparing soleus muscle properties of rats being either hindlimb unloaded or terrestrial deafferented. Under deep anesthesia, a first group of rats were submitted to a bilateral deafferentation (DEAF group, n = 6) performed by section of the dorsal roots L 3 to L 5 after laminectomy. A second group of rats was submitted to a hindlimb-unloading period (HU group, n = 6). After 14 days, the morphological and contractile properties as well as the content in myosin heavy-chain (MHC) isoforms were studied in the right soleus muscle in HU and DEAF groups. The results were compared to those obtained in control animals (CON group). After HU versus CON group, the soleus muscle was atrophied and presented a decrease in muscle forces in relation with a slow-to-fast transition characterized by a decrease in kinetic contractile parameters and by an overexpression in the fast MHC isoforms. The DEAF soleus muscle showed both a significant muscle atrophy and a loss of forces when compared with CON rats. The comparison between DEAF and HU rats indicated that some modifications occurring after HU are purely of motor origin (i.e., slow to fast transition), whereas muscle atrophy and decrease in muscle force are partly the result of an afferent silent. Our study underlined the importance of afferent input integrity in the maintenance of muscle characteristics.

Heme oxygenase-1 and the ischemia-reperfusion injury in the rat heart.

Carbon monoxide (CO) is a signaling gas produced intracellularly by heme oxygenase (HO) enzymes using heme as a substrate. During heme breakdown, HO-1 and HO-2 release CO, biliverdin, and Fe(2+). In this study, we investigated the effects of manipulation of the HO-1 system in an in vivo model of focal ischemia-reperfusion (FIR) in the rat heart. Male Wistar albino rats, under general anesthesia and artificial ventilation, underwent thoracotomy, the pericardium was opened, and a silk suture was placed around the left descending coronary artery; ischemia was induced by tightening the suture and was monitored for 30 min. Subsequently, the ligature was released to allow reperfusion lasting for 60 min. The first group of rats was sham operated and injected intraperitoneally (i.p.) with saline. The second group underwent FIR. The third group was treated ip 18 hr before FIR with hemin (4 mg/kg). The fourth group was pretreated ip 24 hr before FIR and 6 hr before hemin with zinc protoporphyrin IX (ZnPP-IX, 50 microg/kg). Specimens of the left ventricle were taken for determination of HO expression and activity, infarct size, malonyldialdehyde (MDA) production, and tissue calcium content. FIR led to a significant increase in the generation of MDA and notably raised tissue calcium levels. Induction of HO-1 by hemin significantly decreased infarct size, incidence of reperfusion arrhythmias, MDA generation, and calcium overload induced by FIR. These effects were prevented by the HO-1 inhibitor ZnPP-IX. The present experiments show that the concerted actions of CO, iron, and biliverdin/bilirubin modulate the FIR-induced myocardial injury.

Effects of high dose retinoic acid on adult rat liver: electron microscopic and immunohistochemical study

The aim of the present study was to determine the effects of all-trans retinoic acid, a vitamin A metabolite, on liver structure. Twelve adult male rats were used and they were divided into three groups. The first group of rats was fed by gavage 20 mg/kg/day all-trans retinoic acid, whereas second group of rats received 40 mg/kg/day all-trans retinoic acid by gavage for 15 days. The rats in the 3 rd group were used as control. At the end of the study liver tissue samples were taken under ether anesthesia and fixed in Bouin’s and 2.5% glutaraldehyde solution for immunohistochemical and electron microscopic investigations. On light and electron microscopic investigations, we observed sinusoidal dilatation, periportal cellular infiltration, increase of lipid droplets in the Ito cells that correlated to the increase in the amount of all-trans retinoic acid. By immunohistochemical staining, diminished TGF-β2 immune reaction in the hepatocytes of experimental groups and increased immune reaction in the sinusoidal space. However expression of TGF-β2 was significantly increased in hepatocytes of which the infiltrating cells were abundant. As a result we observed that high dose of all-trans retinoic acid disturbed the normal liver structure. Thus, we concluded that structural changes occurred after RA administration was related to the increased dose of the agent and to the interrelation between RA and TGF-β2 level.

Cytotoxic immune response after retroviral-mediated hepatic gene transfer in rat does not preclude expression from adeno-associated virus 1 transduced muscles.

Intravenous delivery of nls-lacZ retroviral vectors to the regenerating liver triggers a cytotoxic immune response directed against transduced hepatocytes. We sought to determine whether prior immunization with retroviral vectors impacted on adeno-associated virus (AAV)-mediated muscular expression of the same transgene. The first group of rats first received nls-lacZ retroviral vectors intravenously after a partial hepatectomy. Thirty days later they received AAV vectors intramuscularly in both legs. In the second group, animals received the same vectors in the opposite sequence (i.e., AAV first and retroviruses 20 days later). In the first group, immune response occurred after retrovirus delivery with appearance of anti-beta-galactosidase antibodies and elimination of transduced hepatocytes. However, the immune response did not prevent sustained (9-month) beta-galactosidase expression in AAV-injected muscles. In the second group, AAV injections did not induce immune response and resulted in beta-galactosidase expression in myofibers. In this group, subsequent delivery of retroviral vectors triggered appearance of immune response and elimination of transduced hepatocytes. However, the immune response did not modify beta-galactosidase expression in AAV-transduced myofibers for up to 9 months. These results demonstrate a differential susceptibility between retrovirally transduced liver and AAV-transduced muscles to immune response against the transgene product.

Histopathological changes in ovary and endometrium after tubal ligation: a rat model.

To evaluate the histopathological effects of tubal ligation on ovary and endometrium in a rat model. Twenty-four female Wistar albino rats weighing 220-260 g were used. The rats were assigned randomly into tubal ligation and control groups. While tubal ligation was applied to the first group of rats, only a laparotomy was performed in the second group. Six weeks later, a second laparotomy was performed and uterine horns and ovaries of the rats in the two groups were excised for histopathological assessment. A pathologist blinded to the groups made histopathological examination including quantification of endometrial phases, presence of endometrial inflammation and counting the number of tertiary follicles and corpora lutea in each ovary. We found no significant difference between tubal ligation and control groups related to the number of tertiary follicles and corpora lutea (p > 0.05). However, in the tubal ligation group, endometrial inflammatory infiltration was significantly higher than in the control group (p < 0.05). Tubal ligation does not affect ovarian histology as an indicator of ovarian function. However, endometrial inflammation may occur after tubal ligation and lead to menstrual irregularities as an early complication.

EXERCISE FOR MITOCHONDRIA

An important source of metabolic inefficiency is a futile cycle of protons across the mitochondrial inner membrane, a process called proton leak. In brown fat, proton leak is catalysed by a protein called uncoupling protein 1(UCP1), and two homologues of this protein have been discovered called UCP2 and UCP3. UCP2 is expressed in most tissues, while UCP3 is expressed mostly in skeletal muscle. Many studies have reported rapid and drastic increases in the level of UCP3 mRNA in skeletal muscle after a single bout of exercise, whilst others demonstrated decreases in UCP3 mRNA during longterm training. It was assumed that these changes had functional significance and that an increase in the level of UCP3 expression could protect muscle cells against elevated substrate supply following exercise by uncoupling substrate oxidation from ATP production, whereas a decrease during long-term training could augment metabolic efficiency. These data suggest changes in the composition of mitochondria in response to exercise such that they display markedly different UCP3 levels, relative to other mitochondrial proteins. Since exercise leads to an increase in the content of mitochondria in muscle fibers, and the expression of UCPs is most probably regulated in a manner similar to that of other mitochondrial proteins, Jones and collaborators hypothesized that UCP3 protein level in skeletal muscle increases during training as part of the increase in the content of mitochondria and that each mitochondrion preserves similar levels of UCP3 proteins. Additionally, they tested whether mitochondria rich type I muscle fibers have higher levels of UCP3 expression than type IIa or IIb fibers that have a lower mitochondrial content.To test their main hypothesis, the authors used rats accustomed to swimming. The exercise protocol consisted of two 3 hour swimming sessions separated by a resting period. The first group of rats performed the protocol for one day, the second for three days and the last group for ten days. The team collected muscle samples after each group's last training session and measured the muscles' UCP3 transcript and protein levels. The transcript level of UCP3 increased very rapidly after a single bout of exercise, while UCP3 protein level displayed a significant increase only after several hours. The level of UCP3 protein increased steadily over 10 days of swimming. Importantly, the increase in UCP3 protein level paralleled that of other mitochondrial proteins, indicating that exercise leads to a rise in the number of mitochondria in the muscle, rather than to a modification in the UCP3 protein content of pre-existing mitochondria.In a separate experiment using sedentary rats, the protein level of UCP3 was compared with that of other mitochondrial proteins in type I, IIa and IIb muscle fibers. The content of UCP3 was higher in type I fibers than in type IIa and IIb fibers, and this pattern is similar to that of other mitochondrial proteins. So the UCP3 protein content of each fiber type parallels their number of mitochondria.Overall, the results presented in this paper support the original hypothesis of the authors and suggest that modification in the expression level of UCPs under certain conditions could reflect changes in the content of mitochondria in cells, possibly due to alteration in cellular energy status.

Histopathological changes in ovary and endometrium after tubal ligation: a rat model

Background. To evaluate the histopathological effects of tubal ligation on ovary and endometrium in a rat model. Methods. Twenty-four female Wistar albino rats weighing 220–260 g were used. The rats were assigned randomly into tubal ligation and control groups. While tubal ligation was applied to the first group of rats, only a laparotomy was performed in the second group. Six weeks later, a second laparotomy was performed and uterine horns and ovaries of the rats in the two groups were excised for histopathological assessment. A pathologist blinded to the groups made histopathological examination including quantification of endometrial phases, presence of endometrial inflammation and counting the number of tertiary follicles and corpora lutea in each ovary. Results. We found no significant difference between tubal ligation and control groups related to the number of tertiary follicles and corpora lutea (p > 0.05). However, in the tubal ligation group, endometrial inflammatory infiltration was significantly higher than in the control group (p < 0.05). Conclusion. Tubal ligation does not affect ovarian histology as an indicator of ovarian function. However, endometrial inflammation may occur after tubal ligation and lead to menstrual irregularities as an early complication.

Effects of lesions of basal forebrain cholinergic neurons in newborn rats on susceptibility to seizures

The cholinergic system modulates cerebral excitability. We recently reported that immunolesions of the basal forebrain (BF) cholinergic neurons in adult rats increase the susceptibility to generalized seizures. In this study we investigated the effects of lesions of the BF cholinergic neurons in neonatal rats on seizure susceptibility and cognitive function. Neonatal rats at postnatal day (P) 7 received intracerebroventricular (i.c.v.) injections of 192 IgG-saporin (SAP) or phosphate-buffered saline. Following 3 weeks after the injection the first group of rats was implanted with hippocampal electrodes for electroencephalogram (EEG) recordings while the second group of rats was tested for visual spatial memory using the hidden platform version of the water maze test. The first group of rats was then tested for seizure susceptibility using flurothyl 1 week after the electrode implantation. Rats that received immunolesions of the BF cholinergic neurons at P7 had significantly shorter latencies to onset of myoclonic jerks and tonic-clonic seizures than controls. However, no significant differences were found in the duration of seizures, or EEG ictal duration. No significant deficits in spatial learning were found between rats that received i.c.v. injections of SAP at P7 and controls. As in adult rats, lesions of the BF cholinergic system in rat pups result in subsequent increase in seizure susceptibility.

Effect of experimental varicocele in rats on testicular oxidative stress status.

The present experiments were undertaken to determine the levels of MDA, SOD and catalase in the testis of adolescent rats with experimental left varicoceles. Male Wistar rats, 7 weeks old and weighing 160-170 g, were randomly allocated into three groups. The first group of rats underwent partial ligation of the left renal vein (n = 15). The second group of rats underwent a sham operation (n = 7) and the third group acted as controls (n = 7). Animals were sacrificed 6 weeks after surgery and dilatation of the internal spermatic veins was observed. Levels of MDA, SOD and catalase activity were measured in testis. The experimental left varicocele group showed severe testicular changes compared to other groups. The mean MDA (SEM) levels in right and left testicular tissues of varicocele bearing rats, sham-operated rats, and control rats were 0.48 +/- 0.24 and 0.31 +/- 0.11, 0.22 +/- 0.02 and 0.35 +/- 0.12, 0.62 +/- 0.29 and 0.13 +/- 0.05, respectively (P > 0.05). The mean SOD (SEM) levels in right and left testicular tissues of varicocele bearing rats, sham-operated rats, and control rats were 7,790 +/- 606 and 6,974 +/- 574, 7,475 +/- 1,517 and 7020 +/- 1,106, 8,727 +/- 1,188 and 9,019 +/- 1,129, respectively (P > 0.05). The mean catalase (SEM) levels in right and left testicular tissues of varicocele bearing rats,sham-operated rats, and control rats were 75.77 +/- 11.5 and 53.82 +/- 10.1, 91.94 +/- 14 and 94.90 +/- 32, 65.40 +/- 5.7 and 90.93 +/- 16.4, respectively (P > 0.05). Our results suggest that oxidative status, which reflects a relative balance between reactive oxygen species (ROS) generated and ROS scavenged, may not be responsible for the testicular dysfunction associated with experimentally induced varicocele during adolescence in rats.

Effect of the GH secretagogue L-163,255 and restricted feeding time on GH pulsatility in the rat.

To determine the effect of repeated treatments with the growth hormone secretagogue (GHS) L-163,255 on the pulsatile release of GH when administered in meal-fed rats before and after feeding. The first group of rats (AL, n=6) had food available ad libitum. The second (restricted, R, n=6), third (GHSB, n=6), and fourth (GHSA, n=6) groups were fed from 1100 to 1400 h. Groups GHSB and GHSA were given GHS by gavage, 3.0 mg/kg L-163,255, at 1000 h (before feeding, B) and at 1500 h (after feeding, A) respectively. Three weeks after the initiation of the treatment, blood samples were collected at 10-min intervals over 6 h, and GH levels were determined. In group R, the concentrations of GH were higher before feeding (17.6+/-2.4 ng/ml) than during feeding (11.2+/-1.2 ng/ml), P<0.05. The average concentrations of the peak in response to GHS were higher when GHS was administered before (121.70+/-33.68 ng/ml) than after (49.67+/-17.87 ng/ml) feeding. The mass of GH, as calculated by deconvolution analysis was also higher in the GHSB group than in the GHSA group (251.6+/-64.1 ng/ml per min vs 85.3+/-22.9 ng/ml per min respectively, P<0.05). L-163,255 is effective in inducing GH release after repeated oral administration in rats. The effectiveness is greater when GHS is administered before rather than after feeding in meal-fed animals.

Lipopolysaccharide causes deficits in spatial learning in the watermaze but not in BDNF expression in the rat dentate gyrus

We investigated the effects of a single injection and a daily injection of lipopolysaccharide (LPS) on spatial learning and brain-derived neurotrophic factor (BDNF) expression in the rat dentate gyrus. LPS is derived from the cell wall of Gram-negative bacteria and is a potent endotoxin that causes the release of cytokines such as interleukin-1 and tumour necrosis factor. LPS is thought to activate both the neuroimmune and neuroendocrine systems; it also blocks long-term potentiation in the hippocampus. Here, we examined the effects of LPS on a form of hippocampal-dependent learning–spatial learning in the water maze. Rats were injected with LPS intraperitoneally (100 μg/kg) and trained in the water maze. The first group of rats were injected on day 1 of training, 4 h prior to learning the water maze task. Groups 2 and 3 were injected daily, again 4 h prior to the water-maze task; group 2 with LPS and group 3 with saline. A number of behavioural variables were recorded by a computerised tracking system for each trial. The behavioural results showed a single injection of LPS (group 1) impaired escape latency in both the acquisition and retention phases of the study, whereas a daily injection of LPS did not significantly impair acquisition or retention. BDNF expression was analysed in the dentate gyrus of all animals. No significant differences in BDNF expression were found between the three groups.

Alteration of the Frank-Starling law in heart failure relates to titin

Alterations of the Frank-Starling relationship under pathological conditions is still a matter of controversy. We investigated this property in perfused whole hearts and in single cells isolated from normal and post-myocardium infarcted (PMI) rats. A balloon connected to a pressure sensor was implanted in the left ventricle, and the intraventricular pressure was monitored following changes in volume. A first group of rats with a very low level of remodeling had a preserved Frank-Starling relationship. The second group, in heart failure, was characterized by tremendous fibrosis and ventricle dilatation, and presented an alteration of the Frank-Starling relationship. ‘Ihe passive and contractile properties of single chemically skinned ventricular cells were measured as well as their length-dependent Ca2’ sensitivity. Cells from failing hearts exhibited a lower stiffness and abnormal tension-pCa properties characterized by a decrease (from 0.4 pCa Unit in control to below 0.2) in the shift of pCa50 induced by a stretch from 1.9 pm to 2.3 nm sarcomere length. Biochemical analysis of contractile proteins was performed. Polyacrylamide gel electrophoresis (2.5-12%) revealed an altered form of titin in the pathological conditions. Based on a previous report showing that the degradation of titin by a mild trypsin digestion resulted in an alteration of the contractility of normal cells (Cazorla et al. 1999), we conclude that the inability of failing hearts to use the Frank-Starling relationship is, in part, attributable to titin alteration.

Combined effects of exposure to styrene and ethanol on the auditory function in the rat

In order to study the auditory effects of a metabolic interaction between ethanol and styrene, a first group of rats was gavaged once a day with ethanol (4 g/kg), a second group was exposed to 750 ppm styrene by inhalation, and a third group was exposed to both ethanol and styrene (5 days/week, 4 weeks). Auditory function was tested by recording brainstem (inferior colliculus) auditory evoked potentials, and cochlear hair cell loss was estimated by light microscopy. Cytochrome P450 2E1 and the main urinary styrene metabolites, namely mandelic, phenylglyoxylic and hippuric acids, were measured by high-performance liquid chromatography to check the effects of ethanol on styrene metabolism. In our experimental conditions, ethanol alone did not have any effect on auditory sensitivity, whereas styrene alone caused permanent threshold shifts and outer hair cell damage. Hearing and outer hair cell losses were larger after the exposure to both ethanol and styrene than those induced by styrene alone, indicating a clear potentiation of styrene ototoxicity by ethanol. As expected, metabolic data showed that ethanol alters styrene metabolism and can therefore be considered a modifying factor of styrene toxicokinetics.

Projection neurons in the superficial layers of the superior colliculus in the rat: a topographic and quantitative morphometric analysis

The present study deals with qualitative and quantitative investigations in the superior colliculus of the rat. Tracer studies were correlated with Nissl staining to calculate the quantitative ratio between projection neurons and interneurons in the upper three layers of the superior colliculus. In order to reveal the projections from the superior colliculus, the first group of rats received injections of the tracer FluoroGold into the nucleus lateralis posterior thalami, the lateral geniculate body, the nucleus parabigeminalis, and the predorsal bundle. Commissural connections between the superior colliculus were traced in a second group of animals, which received Biocytin and FluoroGold injections in the upper layers of the right superior colliculus and small deposits of the carbocyanine tracer DiI in the deeper layers of the left superior colliculus. Additionally, double-labelling with FluoroGold tracing and the histochemical detection of NADPH-diaphorase activity was carried out to distinguish between projection neurons and interneurons. These experiments showed that 66% of the neurons within the superficial layers of the superior colliculus were represented by ascending projection neurons, whereas only 2–3% could be identified as descending neurons. Ascending neurons were scattered throughout the three laminae and descending neurons were localized in a cluster-like pattern. Approximately 2–3% of the neurons in the superficial layers were found to be commissural and interlayer neurons which were represented by an identical cell type, since both transcommissural and interlayer processes were originated from their somata. The somata of these commissural-interlayer neurons were all located in the mediorostral part of the superior colliculus and contained NADPH-diaphorase activity. The axon terminals of the interlayer-commissural neurons formed net-like structures which surrounded neuronal somata within the ipsilateral deep layers and within the contralateral upper layers of the superior colliculus, respectively.

Hemodynamic responses to electrical stimulation of the aortic depressor nerve in awake rats.

Changes in mean arterial pressure (MAP), heart rate (HR), and vascular resistance (hindquarter and mesenteric territories) in response to electrical stimulation (ES) of the aortic depressor nerve (ADN) were evaluated in conscious freely moving rats. Platinum electrodes were implanted into the ADN of all rats studied, and some of these animals were also implanted with miniaturized Doppler probes around the superior mesenteric artery and inferior abdominal aorta (hindquarter). In both groups, the femoral artery and vein were catheterized one day before the experiments. In the first group of rats (n = 7), the control ES of the ADN in the range from 0.5 to 3.0 V (50 Hz, 10 ms) produced bradycardia and hypotension in an intensity-dependent manner, and treatment with methylatropine (intravenously) blocked the bradycardia but produced no significant changes in the hypotensive response. In a second group (n = 6), ES of the ADN was performed with the intensity fixed at 3 V and the frequency of the stimuli varying from 10 to 50 Hz. In this group, the hypotensive response was frequency dependent, whereas the bradycardic response was not. In a third group of rats (n = 6), ES of the ADN (2.5 V) produced hypotension (-35 +/- 4 mmHg), minor changes in the mesenteric (+5 +/- 14%), and vasodilation in hindquarter (-32 +/- 6%) vascular beds. The data show that 1) ES of the ADN produces a fall in pressure, bradycardia, vasodilation in the hindquarter, and no changes in the mesenteric vascular resistance, 2) methylatropine blocked the bradycardia and produced no effect on the hypotensive response to ES of the ADN, and 3) the baroreceptor afferent fibers involved in the hypotensive response to ES of ADN are sensitive to the variation of the frequency of the stimuli, whereas the fibers involved in the bradycardic response are not.

Biodistribution and Imaging of Polyethyleneimine-A Gene Delivery Agent

Polyethyleneimine (PEI) has been described as a potentially effective agent for gene delivery. To track the delivery of this gene vector, the biodistribution and imaging of PEI labeled with 111Indium (111In) was studied in Fischer 344 rats. PEI was conjugated with diethylenetriamine pentaacetic acid dianhydride (DTPA), dialyzed, and chelated with 111In. Breast adenocarcinoma 13762 tumor cells were inoculated into the thighs of the rats. The first group of rats (n = 3) were injected intravenously with 300 mu g of the Indiumlabeled DTPA-polyethlyeimine (111In-DTPA-PEI) (50 mu Ci per rat) or 111In-DTPA. These animals were imaged with a gamma camera with a medium energy parallel hole collimator at 5 min, 2 hr, and 24 hr postinjection. The percentage of uptake in tumor (region of interest) was quantitated by a computer image analyzer and expressed as a percentage of injected dose (%ID) per pixel. To further characterize the tissue distribution of 111In-DTPA-PEI (300 mu g, 10 mu Ci per rat) and 111In-DTPA (10 mu Ci per rat), a second group of animals (n = 18) bearing breast tumors were studied with tissue uptake quantified at 2 hr, 24 hr, and 48 hr using a gamma counter. In addition, autoradiography was used to further characterize the distribution of the labeled polymer in two rats at 2 and 24 hr. From these studies, PEI was found to be rapidly cleared, primarily through the kidneys of the rats. In addition, the distribution of 111In-DTPA-PEI was found to be significantly different from 111In-DTPA with a higher tumor-to-blood ratio. These studies show that radio-labeled PEI may have potential as a gamma scintigraphy imaging agent and in tracking the delivery of genetic material.

Effect of 50% Small Bowel Resection on Gastric Prostaglandin E 2 Levels in Rats

The mechanism for the production of increased gastric secretion following massive intestinal resection is not clearly defined. The loss of an intestinal inhibitor has been most frequently suggested to explain this hypersecretion. The role of endogenous prostaglandins which can inhibit gastric secretion is not established. The present study was undertaken to determine the effect of 50% proximal small bowel resection on Prostaglandin E 2 (PGE 2) levels in rat gastric mucosa. This study was performed in 30 rats divided into three groups. The first group of rats served as unoperated controls, the second group was sham operated and the third group underwent 50% resection of proximal small intestine. The PGE 2 levels in rat gastric mucosa was decreased significantly (p < 0.001) in the resection group (422.85 ± 7.66 pg/gm) as compared with the sham group (478.77 ± 7.25 pg/gm) and the control group (493.38 ± 4.61 pg/gm). Total gastric acidity was increased significantly (p llt 0.001) in the resection group (63.05 ± 2.64 mEq/L) as compared with the sham group (15.21 ± 0.99 mEq/L) and the control group (17.19 ± 0.80 mEq/L). The PGE 2 levels and total gastric acidity were not significantly changed in either the control or sham operation groups (p > 0.05). The results suggest that endogenous prostaglandin synthesis has a regulatory role in gastric hyperacidity after 50% proximal small bowel resection in rats.